; 967 
>py 1 



Issued May 0, 1913. 

U. S. DEPARTMENT OF 'AGRICULTURE, 

BDREAU OF CHEMISTRY— BDLLETIN No. 165. 

CARL L. ALSBP:RG, Chief of Bureau. 



LEATHER mVESTIGATIOl^S: 

THE COMPOSITION OF SOME 
SOLE LEATHERS. 



BT 

F. P. VEITCH, 

Chief Leather and Paper Laboratory, 

AND 

J. S. ROGERS, 

Assistant Chemist. 




WASHINGTON: 

GOVERNMENT PRINTING OFFICE. 

1913. 



ORGANIZATION OF BUREAU OF CHEMISTRY. 



Carl L. Alsberg, Chief of Bureau. 

W. D. BiGELOW, Assistant Chief of Bureau. 

F. B. Linton, Chief Clerk. 

G. O. Savage, Editor. 

A. E. Draper, Librarian. 
Division of Foods, W. D. Bigelow, Chief. 

Food Technology Laboratory, E. M. Chace, Chief and Assistant Chief of Division. 

Oil, Fat, and Wax Laboratory, H. S. Bailey, Chief. 
Division of Food Inspection, L. M. Tolman, Chi^f. 
Division of Drugs, L. F. Kebler, Chief. 

Drug Inspection Laboratory, G. W. Hoover, Chief. 

Synthetic Products Laboratory, W. O. Emery, Chief. 

Essential Oils Laboratory, E. K. Nelson, Chief. 

Pharmacological Laboratory, Wm. Salant, Chief. 
Chief Food and Drug Inspector, W. G. Campbell. 
Miscellaneous Division, J. K. Haywood, Chief 

Water Laboratory, W. W. Skinner, Chief. 

Cattle Food and Grain Laboratory, G. L. Bidwell, Chief 

Insecticide and Fungicide Laboratory, C. C. McDonnell, Chief. , 

Trade Wastes Laboratory, under Chief of Division. 
Animal Physiological Laboratory, F. C. Weber, Chief. 
Bacteriological Laboratory, G. W. Stiles, Chief. 
Contracts Laboratory, P. H. Walker, Chief. 
Dairy Laboratory, G. E. Patrick, Chief. 
Enological Laboratory, W. B. Alwood, Chief. 
Food Research Laboratory, M. E. Pennington, Chief. 
Leather and Paper Laboratory, F. P. Veitch, Chief. 
Microchemical Laboratory, B. J. Howard, Chief. 
Nitrogen Laboratory, T. C. Trescot, Chief. 
Physical Chemistry Laboratory, C. S. Hudson, Chief. 
Plant Chemistry Laboratory, J. A. Le Clerc, Chief. 
Sugar Laboratory, A. H. Bryan, Chief. 
Food and Drug Inspection Laboratories: 

Boston, A. L. Sullivan, Chief. 

Buffalo, W. L. Dubois, Chief. 

Chicago, A. L. Winton, Chief. 

Cincinnati, B. R. Hart, Chief. 

Denver, R. S. Hiltner, Chief. 

Detroit, H. L. Schulz, Chief. 

Galveston, . 

Honolulu, Hawaii, A. W. Hansen, Acting. 

Kansas City, Mo., F. W. Liepsner, Chief. 

Nashville, R. W. Balcom, Chief. 

New Orleans, W. J. McGee, Chief. 

New York, R. E. Doolittle, Chief. 

Omaha, S. H. Ross, Chief. 

Philadelphia, C. S. Brinton, Chief. 

Pittsbiurgh, M. C. Albrech, Chief. 

Portland, Oreg., A. L. Knisely, Chief. 

St. Louis, D. B. BiSBEB, Chief. 

St. Paul, A. S. Mitchell, Chief. 

San Francisco, H. M. Loomis, Chief. 

San Juan, P. R., A. E. Taylor, Acting. 

Savannah, W. C. Burnet, Chief. 

Seattle, R. W. Hilts, Chief. 



Issued Miiy 6, l'J13. 

U. S. DEPARTMENT OF AGRICULTURE. 

BUREAU OF CHEMISTRY— BULLETIN No. 165. 

CARL L. ALSBEKG, Chief of Bureau. 



LEATHER INVESTIGATIONS: 

THE COMPOSITION OF SOME 
SOLE LEATHERS. 



F. P. VEITCH, 

Chief Leather and Paper Laboratory, 



J. S. ROGERS, 

Assistant Chemist. 




WASHINGTON: 
GOVERNMENT PRINTING OFFICE. 

1913. 






a OF D. 



j\a 




LETTER OF TRANSMITTAL 



U. S. Department of Agriculture, 

Bureau of Chemistry, 
Washington, D. C, November 20, 1912. 
Sir: I transmit for your inspection and approval manuscript 
entitled "Leather Investigations: The Composition of Some Sole 
Leathers," by F. P. Veitch and J. S. Rogers. The results which 
have been obtained show that weighting of leathers with useless or 
harmful materials is extensively practiced. The country's resources 
in leather materials are thus wasted and the pubHc defrauded. I 
recommend that this be published as Bureau of Chemistry Bulletin 
No. 165. 

Respectfully, R. E. Doolittle, 

Acting Chief of Bureau. 
Hon. James Wilson, 

Secretary of Agriculture, 



CONTENTS, 



Pag©. 

Composition of nonnal sole leather 7 

Weighting of leather 8 

Weighting materials and their effects 9 

Quantity of added weighting materials 10 

Waste of materials in weighting sole leather 10 

Detection of weighting 11 

Bleaching of sole leather 12 

Misbranding of leather 13 

Prevention of weighting and bleaching 14 

Results of analysis 15 

Summary 20 

6 



LEATHER INYESTIGATTONS: THE COMPOSITION OF 
SOME SOLE LEATHERS. 



COMPOSITION OF NORMAL SOLE LEATHER. 

Vegetable-tanned leather is essentially a compound or mixture of 
hide or fibrous proteid material with tannin. Depending on the use 
to which it is to be put, it may be finished in several ways whereby 
the composition of the final product may differ greatly from the 
simple compound. The tanned leather may be used without material 
change in composition, as for shoe soles; it may be greased, as for 
harness and belting; or it may be greased and dyed, as for harness 
and shoe uppers. 

In addition to the insoluble hide and tannin which are the 
essential constituents of leather, moisture, mineral matter, fats, and 
water-soluble tanning materials, which remain to a small extent in 
well-scoured leather, are present. All of these, when not present 
in excessive quantities, are proper and normal constituents of the 
leather. In fact, the presence of a large percentage of oUs or fats, 
even in sole leather, is of decided advantage in increasing the water 
resistance, flexibility, softness, and life of the leather, while the pres- 
ence of a small amount of uncombined tannin is often of some advan- 
tage in retarding water penetration and hardening of the leather and 
in making it solid and firm. The presence of a large excess of uncom- 
bined tannin materials other than those mentioned is useless or 
harmful. 

Leather is not a definite compound and is therefore impossible to 
produce of an exact composition. The ratio of combined tannins to 
hide substances approximates 7 to 10 (see last column of table on 
pp. 16 to 20), while the percentages of water-soluble constituents, min- 
eral matter, fat, and moisture may vary considerably. Careful study 
of the analyses of well-tanned, scoured leathers of various tannages, 
both American and foreign, warrants the conclusion that weU-tanned, 
merchantable, scoured sole leather of all tannages on analysis should 
give results on a moisture-free basis which fall between the following 
limits: Leather substance from 75 to 93 per cent, hide substance from 
43 to 57 per cent, combined tannins from 31 to 42 per cent, water- 
soluble materials from 5 to 15 per cent, oils and fats from 1 to 6 per 
cent, ash from 0.25 to Iper cent. 



8 LEATHER INVESTIGATIONS : SOLE LEATHERS. 

Well-tanned, honestly-made leather should approach the upper 
rather than the lower limits for leather substance and oils and fats. 
The water-soluble constituents should consist only of the materials 
contained in the adhering tanning solution which have not been 
removed in scouring. 

Properly air-dried sole leather should not contain, even in very 
damp weather, more than 20 per cent of moisture, and the average 
percentages for the year should fall below 15 per cent. Neither the 
ultimate buyer nor the shoe manufacturer should be called upon to 
pay for a greater average amount than this. It will be observed that 
the leathers reported herewith contain much less moisture, due largely 
to the fact that they dried out very much after reaching the laboratory. 

Normal vegetable-tanned sole and harness leather when burned 
should not leave more than 1 per cent of ash and as a rule not more 
than 0.5 per cent. This ash is derived from the hide, from the 
lime used in unhairing, and from the salts usually dissolved in aU 
waters. The magnesia of the ash when calculated to Epsom salts 
(MgS04 + 7H20), the form present in air-dried leather, should not 
exceed 1 per cent. 

It is customary abroad to consider less than 2 per cent of glucose 
permissible, the assumption being that this amount may be present 
from the tanning materials. . It is very doubtful if this amount of 
glucose is ever present in normal leathers from which the excess of 
tanning materials has been properly washed. Leathers on which the 
final liquors were sweet and exceptionally concentrated, and which 
are subsequently washed but little, may contain between 1 and 2 per 
cent of sugars, determined as dextrose. 

The ether extract or fat may be as high as 5 per cent, probably 
never much less, to give pliability, water resistance, and durability to 
the leather. 

WEIGHTING OF LEATHER. 

During an extended examination of sole leathers now in progress, 
it has been found that a surprisingly large percentage contains great 
quantities of foreign materials. Although it has long been known 
that some tanners make a practice of weighting or loading their 
leather, the extent of the practice is not appreciated outside the 
tanning and closely related industries. Tanners state that leather is 
loaded with foreign materials because the boot and shoe makers will 
buy only the lower-priced leather, which, to use a trade expression, 
''cuts to advantage," that is, from which the greatest number of soles 
can be cut at the lowest cost a pair. Many boot and shoe manufac- 
turers claim that they use loaded leather because it cuts to better 
advantage than the same leather not loaded. 

The character, value, and wearmg quahty of leather varies with 
the part of the skm from which it is made. The skin from the upper 



WEIGHTING OF LEATHER. 9 

part of the body and along the back is closer fibered than that from 
the lower part, under the body; it becomes more open textured and 
consequently more porous as it passes from the backbone to the 
under side of the body. The skin over the posterior portion of the 
body is of closer texture than that over the forequarters; conse- 
quently the best leather is made from the hide in the region of the 
kidneys and hips, provided the skin is sound and not damaged in 
tanning. The leather from the ''flanks" and "beUics" is more 
porous, lighter, and more flexible than that made from the "back,^' 
and in cutting the side of leather into soles the lighter and more 
flabby the lower portions the more of it is rejected. If, however, 
this lower portion has been stiffened and weighted with foreign 
material, no matter how useless it is nor how soon it may wash out, 
some shoe manufacturers will cut it into soles, thus obtaining more 
soles from a side. Because of these facts the shoe manufacturers cal- 
culate that weighted leather costs them less for each pair of soles than 
the unweighted leather. 

Unloaded flabby leather makes poor shoe soles, and loading with 
materials readily soluble in water, as glucose and Epsom salts, in- 
creases the cost to the purchaser, and does not make soles more 
serviceable. 

WEIGHTING MATERIALS AND THEIR EFFECTS. 

Loading or weighting materials are cheap. Those in most general 
use in this country are glucose, selling at 2 cents a pound; Epsom 
salts, or magnesium sulphate, selling at 1 cent a pound; and solutions 
of tanning or other organic materials, selling at 0.75 to 2 cents a pound. 
Barium sulphate and lead sulphate — generaUy formed by drumming 
the leather first in a solution of barium chlorid, costing 2 cents a 
pound, or of sugar of lead at 9 cents a pound, and then in sulphuric 
acid — and sodium sulphate, costing 1 cent a pound, are also employed 
to a small extent. Of these loadmg materials, glucose, soluble 
organic materials containing little or no tannin, magnesium sulphate^ 
barium sulphate, lead sulphate, and sodium sulphate are much more 
objectionable than a small excess of actual tanning material. 

Loadmg with glucose, Epsom salts, barium sulpha^te, lead sulphate, 
excessive quantities of tanning materials, or with water-soluble 
organic material is often detrimental to leather. It is made hard, 
brittle, more likely to crack, and after the loading washes out, as 
usually happens quite readily except m the case of barium and lead 
sulphates, it is more easily penetrated by water. Loaded leathers are 
more expensive, less durable, and a menace to health. A distinction 
should possibly be made between >the effects of an excess of true 
tannin and of other uncombined or loading materials. The excess of 
true tannin may not itself be so objectionable and may even be of 
70416°— Bull. 165—13 2 



10 LEATHEE INVESTIGATIONS: SOLE LEATHERS. 

temporary advantage, because the slowly soluble tannins make the 
leather more water resistant and impede the removal of combined 
tannin from the leather. 

QUANTITY OF ADDED WEIGHTING MATERIALS. 

The amounts of materials found in the loaded leathers examined 
are summarized as follows: Ash, from 0.2 to 2.7 per cent; ether 
extract, from 0.4 to 5.6 per cent; Epsom salts, from 0.2 to 7.5 per 
cent; glucose, from 0.2 to 12.4 per cent; water-soluble materials, from 
13.4 to 34.3 per cent; water-soluble tannin, from 6.1 to 17.8 per cent. 

If it is feasible to secure the lower figures, as it appears to be in a 
number of tanneries, the higher figures must represent very excessive 
quantities. A comparison of these, together with those in the table 
on pages 16 to 20, with the figures given for normal leathers shows that 
the percentages of ash, Epsom salts, glucose, and water-soluble mate- 
rials are, as a rule, above the permissible quantities, while the amounts 
of fats and oils and actual leather substance are lower than they 
should be. These figures show a serious moral, economic, and busi- 
ness condition. Approximately 63 per cent of the leathers examined 
are weighted with glucose, Epsom salts, or both. This loading varies 
from 1 to 7.5, with an average of 3, per cent of Epsom salts, and up to 
10.4, with an average of 5.5, per cent of glucose, and amounts to a^ 
total maximum loading, when both are present, of 16 per cent and an 
average of 8 per cent. 

WASTE OF MATERIALS IN WEIGHTING SOLE LEATHER. 

The tanners whose leathers have been examined produce a large 
percentage of the sole leather made in this country. It seems prob- 
able, therefore, that these samples are fairly representative of Amer- 
ican sole leather, and if this be true fully 60 per cent of the sole 
leather is loaded with Epsom salts or glucose or both, and practically 
all of it contains more uncombined tanning materials than it should. 

If 60 per cent of the sole leather contains an average of 8 per cent 
of Epsom salts and glucose, at least 150,000,000 pounds have been 
weighted annually with no improvement in its wearing value. The 
people have paid for not less than 12,000,000 pounds of Epsom salts 
and glucose, plus a profit to the tanner for working them into the 
leather, and have obtained nothing of value thereby. The average 
amount of water-soluble material in these sole leathers is 23 per 
cent. Subtracting from this the average percentage of glucose and 
Epsom salts found gives the percentage of what for brevity may be 
called "uncombined tanning" materials, meaning the materials 
derived from the tanning liquors in which the leather was tanned. 

The almost universal practice of weighting or loading with excessive 
quantities of uncombined tanning materials is perhaps the most repre- 



WEIGHTING OF LEATHER. 11 

hensible form of* weighting. It is needless and wastes valuable mate- 
rials which can be employed in the production of more leather, and it 
often leads to bleaching or addition of glucose or Epsom salts to con- 
ceal the mjury which frequently results from the presence of excessive 
quantities of uncombmed tanning materials. The elimhiation of this 
waste would not only conserve our fast-duninishing native tanning 
materials, but reduce the quantity imported, and thus help maintain 
the balance of trade in favor of this country. It is an astonishing 
fact that practically all the leathers analyzed contain as much uncom- 
bined tannin as good quality oak or hemlock bark and many contain 
much more. Inspection of the tables shows that approximately one- 
third of the tannin in these leathers is uncombined, the quantity 
varying from 9 to 17 per cent. This is sufficient to tan one-third 
as much sole leather as is now made. Fully half of this wasted tannm 
can and should be saved. It is worth approximately $1,000,000 
and would tan approximately 100,000,000 pounds of leather. This 
tanning material is now practically a total loss. 

For the past 15 or 20 years energetic efforts have been made to 
prepare from the waste liquors produced by making paper from wood 
by the sulphite process products that will tan hides. The woods 
from which paper pulp is made, with but few exceptions, do not con- 
tam more than from 2 to 4 per cent of tannm. If this is all removed 
by the sulphite liquors which are subsequently concentrated to 50 
per cent solids, the concentrated material offered for tanning purposes 
can contain at most but 4 or 5 per cent of tannin. Up to the present 
efforts to make leather with waste sulphite liquors have been crowned, 
at most, with but indifferent success, and in no case do the makers of 
these products from sulphite liquors advocate that they be used alone 
in tanning, but always in mixture with materials of known tanning 
value. These materials are now receivmg careful attention from 
several sources for determining fuiaUy whether they have a proper 
place in the making of leather. Until such time as it shall have been 
shown that these products will make serviceable leather or that the}' 
contribute to the desirable qualities of leather they should not be 
used in commercial tanning. 

DETECTION OF WEIGHTING. 

Although it is not practicable for the ordin; jy individual to deter- 
mine whether the leather in shoes has been weighted or loaded, the 
shoe manufacturer can do so in a very simple way. Large quantities 
of Epsom salts give leather the characteristic bitter taste of the salts, 
while glucose in quantity gives the leather a very faint sweetish taste. 

Whether or not leather has been loaded with soluble materials can 
be readily determined by anyone by the following simple procedure: 
Grind a sample of the leather (a pair of soles serves well) to a 



12 



LEATHEE INVESTIGATIONS: SOLE LEATHERS. 



coarse powder in any convenient way. The leather may be rasped, 
cut with a chisel or shears, ground in a mill, or sawed. Weigh 100 
grams of the ground leather on a scale that will weigh accurately to 
1 gram. Place it in a small, dry, close-textured cotton bag which 
has been washed to remove the starch and other dressing materials 
from the fabric and which has been given an identifying mark which 
will not wash out in hot water. Tie securely the mouth of the bag, 
weigh the bag and leather carefully, and record the weight. Place it 
in running water as hot as can be readily borne by the hand, and 
wash out the soluble materials by thorough kneading for 15 minutes. 
Squeeze out the water and dry over the radiator or in any convenient 
way until the leather is perfectly dry. Cool and weigh again. The 
loss in weight represents the amount of soluble matter which has 
been washed out. This loss in grams, as thus determined directly 
represents also the percentage loss, and if this exceeds 15 per cent 
the leather may safely be said to be weighted. 

The following figures show some results actually obtamed by this 
method and also the results obtained in careful analysis of the 
leather: 

Water-solubh material in leather. 



Sample No. 


Water-soluble material. 


Regular 
analysis. 


^^' ashed 
out in 10 
minutes. 


V\' ashed 
out in 20 
minutes. 

Per cent. 
20 
24 
34 
24 


2119 
2127 
2130 
2134 


Per cent. 
25 
28 
32 
25 


Per cent. 

20 

. 24 

34 

24 



For practical purposes the results obtamed in tliis way are suf- 
ficiently accurate. 

BLEACHING OF SOLE LEATHER. 

Leather which has been properly tanned with liquors made from 
chestnut or rock oak bark has been considered for generations to be 
the best for shoe soles. This leather has a bright light-oak color, 
the price which it brmgs depending very largely on this brightness 
and uniformity of color. As it comes from the tanning liquors 
leather is often quite irregular in colormg, and when made from 
nearly all other vegetable tanning materials it is darker in color than 
that tanned with oak bark. Irregularity of color is not necessarily 
a sign of mferiority, but, as a matter of fact, it generally indicates 
damage done in the preparation, tannmg, or finishing of the leather, 
or stained or damaged places on the original hides. The shoe manu- 
facturer knowing that uniform color is characteristic of hides prop- 



MISBKANDING OF LEATHER. 13 

erly prepared, tanned, and finished, and that oak bark makes a 
bright-colored leather, demands light, uniformly colored sole leather. 
The wearer of shoes also prefers leather with a good, clear, even 
color. 

To secure the higher price which this much-desired uniformity, 
brightness of color, and the appearance of oak-tanned leather brings 
the leather is bleached. Solutions of soda and sulphuric acid applied 
successively, oxalic acid, or oxalic acid and tinchlorid are the chemicals 
with which this is usually done. The treatment removes some of the 
excess tanning material from the surface and gives the leather a 
much lighter color. Bleaching is especially detrimental, as the 
sulphuric acid is rarely completely neutralized and consequently 
greatly hastens the rotting of the leather. The cost of the leather is 
increased by this procedure; the serviceability of the leather is 
decreased; and the superior appearance secured in this way permits 
the fraudulent sale of the leather at a higher price. The bleaching of 
heavy leather is the most useless and harmful of all leather-making 
practices, and the most vigorous efforts should be made to eliminate it. 

MISBRANDING OF LEATHER. 

Formerly all sole leather made m this country was tanned with 
oak or hemlock bark or a mixture of the two, and the leather so tanned 
was known as oak, hemlock, and union (oak and hemlock), respec- 
tively. More leather is tanned now with quebracho than with oak, 
and more with quebracho, mangrove, myrobalan, gambler, and 
chestnut, collectively, than with hemlock. Nearly half of the 
vegetable-tanned leather made in this country is tanned with 
materials other than oak and hemlock bark. Nevertheless, practi- 
cally all vegetable-tanned leathers are still termed oak, hemlock, or 
union. 

The figures in the table (pp. 16 to 20) show that many of the leathers 
are misbranded as to tannage. The tannm-free wat®r extract from a 
leather tanned with chestnut oak is fluorescent when made faintly 
alkaline. It will be seen that the water solubles from some of the 
so-called oak leathers are not fluorescent; these leathers were not 
tanned with chestnut oak. The figures for water-soluble materials also 
show that many of these leathers were tanned with tanning materials 
other than oak or hemlock bark. Tanning liquors made from nearly 
all materials now used in this country, such as oak, hemlock, and 
mangrove barks, chestnut and gambler extracts, and myrobalan, 
contain approximately 2 parts of tannin to 1 part of nontanniu, 
not including in the nontannin the sugars which the materials contain, 
which are fermented to acids and do not, therefore, add du-ectly to 
the weight of the leather. Quebracho extract, on the other hand, 
contains approximately 7 parts of tannm to 1 part of nontannin. 



14 LEATHEK INVESTIGATIONS : SOLE LEATHEES. 

In the last stages of tanning, the leather is in contact with practi- 
cally fresh normal liquors in which the relations just stated hold. 
Therefore the tannins and nontannins of the water-soluble extracts 
from leather will tend to approximate the same ratio to each other as 
the liquors in which it was tanned. If the sum of glucose and 
magnesium sulphate is subtracted from the figures for the non- 
tannins in any particular leather, the difference approximates the 
nontamiin figures for the liquor in which the final tannmg of the 
leather was conducted. A comparison of this figure with the figures 
for soluble tannin shows the ratio of tannin to nontannin in the 
liquor, and in many instances proves conclusively that tanning 
materials other than oak or hemlock bark were used. In fact, the 
ratio indicates that quebracho was used, but no intimation of the 
fact is given in the branding of the leather. The branding of all 
leathers — "oak," "hemlock," or "union" — is deceptive and the 
practice should be discontinued. No leather should be branded oak, 
hemlock, or union which is not tanned entirely with oak or hem- 
lock or a mixture of the two. 

The misbrandmg of leather is indicated by the recent census 
statistics. The percentage of oak leather reported in 1909 is 7 per 
cent greater than in 1904; the percentage of union leather is 32 
per cent greater in 1909 than in 1904; while the quantity of hemlock 
and oak barks and extracts used in 1909 is materially less than in 
1904. 

PREVENTION OF WEIGHTING AND BLEACHING. 

It is improbable that the present practices of weighting and 
bleaching sole leather will be voluntarily discontmued by the tanner. 
Intelligent buying on the part of the public will do much to break 
up these practices. The individual purchaser of course can not 
know whether the leather m the shoes he buys is weighted or has 
been bleached, but if he will msist that they shall not be made of 
weighted or bleached leather and will not buy from those manu- 
facturers who make such leather, the quantity of leather so treated 
will materially decrease, and it will be found that shoes are more 
durable and consequently less expensive. 

The weighting and bleaching of leather may be easily and abso- 
lutely controlled by concerted action on the part of the shoe manu- 
facturers. It is very simple for them to determine whether the sole 
leather delivered is weighted, and if they will refuse to buy such 
leather it will not be made. Shoe manufacturers will see to it that 
sole leather is not weighted if the public will take sufficient interest 
in the matter to demand unweighted leather. 



RESULTS OF ANALYSIS. 



15 



RESULTS OF ANALYSIS. 

In the following list are given the names of the known tanners of 
the samples examined. These tanning firms are among the most 
representative producers of sole leather in this country. Probably a 
number of the leathers, the source of which is not known, were tanned 
by these known firms, but there is reason to think that many of them 
were produced by other tanners of sole leather. 



MANUFACTURERS OF LEATHER. 



Allen, N. R., & Sons, Kenosha, Wis. 
American Oak Leather Co., Cincinnati, 

Ohio. 
Cover & Co., Philadelphia, Pa. 
Deford, The, Co., Baltimore, Md. 
England-Walton Co., Philadelphia, Pa. 
Harrington, Frederic, Dunnellon, N. Y. 
Howes Bros., Boston, Mass. 
Janney & Borrough, Philadelphia, Pa. 
Kistler Lesh Co., Boston, Mass. 
Leas & McVitty, Philadelphia, Pa. 
McAdoo & Allen, Philadelphia, Pa. 

The analytical results, so far as they are indicative of weighting 
or the presence of useless or harmful materials, are given in the follow- 
ing table: 



Mooney, W. W., & Sons, Columbus, Ind. 
Pfister & Vogel Leather Co., Milwaukee, 

Wis. 
Rippman & Sons, Millerstown, Pa. 
Smoot, C. C, & Sons, Alexandria, Va. 
Toxaway Tanning Co., Rosman, N. C. 
U. S. Leather Co., New York, N. Y. 
Vaughan, Geo. C, Salem, Mass. 
Vulcano Tanning Co., Boston, Mass. 
Wilkinson, Rieger & Jones, Philadelphia, 

Pa. 



16 



LEATHER INVESTIGATIONS : SOLE LEATHERS. 



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RESULTS OF ANALYSIS. 19 

The leathers here analyzed were secured from various sources; some 
were sent by tannere, some by shoemakers, some by sole cutters, 
and others were purchased from dealers. In some cases it was 
impossible to learn who tanned the leather; in the other cases the 
name of the tanner was given by the dealer, or his trade-mark or 
name appeared on the leather. Beyond this nothing is known as 
to the source of the leathers. 

In the third column the approximate date of receipt of the leather 
is indicated. It will be observed that many of these samples are 
5 or 6 years old. Comparison with samples taken more recently 
does not indicate material change in tannery practice with respect 
to loading. 

Referring to the tables, the "Moisture" consists of the water 
which the leather exposed to the air naturally contains in addition 
to aU the water of crystallization of any Glauber's salts, or sodium 
sulphate, and five-sevenths of the water of crystallization of any 
Epsom salts, or magnesium sulphate, which may be in the leather. 

In the column headed "Ash" are given the residues from burning 
the leather. These residues include the ignited, dehydrated soluble 
salts which may have been in the leather, such as Epsom and Glau- 
ber's salts. 

Parker ^ has shown in an extended investigation that the insoluble 
ash of sole and harness leathers, even though they be heavily weighted 
with soluble salts, averages less than 0.2 per cent, and very rarely 
exceeds 0.3 per cent. As none of these leathers was weighted with 
insoluble minerals, in those cases where the ash exceeds 0.3 per cent 
such excess is included as part of the total water-soluble material 
and so treated in calculating the combined tannin. 

The column headed "Petroleum ether extract" shows the percent- 
age of fats and greases which the various leathers contain. 

The "Water soluble material" embraces soluble tannins and non- 
tannins. The latter include glucose, Epsom salts (minus five- 
sevenths of its water of crystallization, which is included under mois- 
ture), and practically aU but about 0.3 per cent of the ash. The sum 
of the moisture, insoluble ash (assumed here to be 0.3 per cent), 
total water soluble, and the liide substance (calculated from the deter- 
mination of nitrogen) subtracted from 100 approximately equals the 
combined tannin, which is combined with hide to form leather. 

The figures for Epsom salts show the amount of this salt (MgSO^-f- 
THoO) present in the air-dried leathers. The column headed "Glu- 
cose" shows the amounts of water-free glucose and dextrin which the 
leathers contained, calculated as dextrose. In the last column is 
given the ratio of combined tannin to hide; that is, the number of 
parts of tannin combined with 1 part of hide to form leather substance. 

> J. Soc. Chem. Ind., 1910, S9: 315. 



20 LEATHER INVESTIGATIONS: SOLE LEATHERS. 

As will be seen, this quantity does not vary greatly from 0.7 part. 
In those cases where it is materially greater, it is probable that the' 
leather contained many difficultly soluble reds, or uncombined 
tannins which were not completely extracted from the leather. 

SUMMARY. 

A large majority of the samples examined contained an unneces- 
sary quantity of uncombined tanning material. But little less than 
$1,000,000 worth of tannin is wasted annually in this way. 

Sixty-three per cent of the leathers examined were weighted with 
glucose, with Epsom salts, or with both. The quantity of loading 
varied from 1 to 7.3 per cent of Epsom salts, with an average of 3 per 
cent. The maximum quantity of glucose in the loaded leathers 
was 10.4 per cent and the average 5.5 per cent. The maximum 
amount of these loading materials found in any leather was 16 per 
cent and the average where both were present was 8 per cent. The 
results obtained indicate that not less than 12,000,000 pounds of 
glucose and Epsom salts are sold annually in sole leather to the 
American people. 

The materials add absolutely nothing to the wearing value of the 
leather and where present in large quantity may positively decrease 
its wear. Shoes made from these leathers are readily penetrated 
by water. Loading makes leather more costly, consequently an infe- 
rior leather costs more than a good leather. 

Leather-making raw materials are wastefully consumed, the product 
may be inferior, the cost increased, and health is endangered by the 
prevalent practices of weighting and bleaching sole leather. 



ADDITIONAL COPIES of this publication 
-t\- may be procured from the Superintend- 
ent OF Documents, Government Printing 
Office, Washington, D. C. , at 6 cfnts per copy 




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